MEMS micromirror structure and preparation method thereof

Abstract

The present disclosure relates to the technical field of micro-electro-mechanical system, and particularly relates to a MEMS micromirror structure and a preparation method thereof, wherein a support structure is bonded to a top surface of a substrate; a torsional beam is fixedly connected with the support structure, and a mirror is fixed to a middle part of the torsional beam and is divided into a first part and a second part by the torsional beam; a first interdigital electrode is located on a side of the first part away from the torsional beam, and the first interdigital electrode comprises first fixed electrodes and first movable electrodes which are alternately distributed in sequence in a direction away from the first part and have uneven top surfaces; a second interdigital electrode is located on a side of the second part away from the torsional beam, and the second interdigital electrode comprises second fixed electrodes and second movable electrodes which are alternately distributed in sequence in a direction away from the second part and have uneven top surfaces; the first movable electrodes and the second movable electrodes are used to be tilted by being applied with opposite driving forces, and drive the mirror to rotate around the torsional beam by a preset angle. At least in the case of providing the same driving force, the driving voltage for driving the micromirror structure can be reduced.

Description

Technical Field

[0001] This disclosure relates to the field of micro-electro-mechanical systems (MEMS) technology, and in particular to a MEMS micromirror structure and its fabrication method. Background Technology

[0002] Microelectromechanical systems (MEMS) micromirrors, as core components of optical scanning, have been widely used in fields such as LiDAR, projection displays, biomedical imaging, and optical communication. Their driving methods mainly include electrostatic, electromagnetic, piezoelectric, and thermal actuation, among which electrostatic comb-driven actuation has become the mainstream solution due to its low power consumption, fast response, and good process compatibility.

[0003] However, traditional MEMS micromirror structures require a large driving force to generate electrostatic force in the vertical direction, which limits the performance improvement and size reduction of MEMS micromirrors. Summary of the Invention

[0004] According to various embodiments of this disclosure, a MEMS micromirror structure and its fabrication method are provided, which can reduce the driving voltage used to drive the micromirror structure without increasing the volume of the fabricated product or providing the same driving force.

[0005] According to some embodiments, a first aspect of this disclosure provides a MEMS micromirror structure, including a substrate, a support structure, a torsion beam, a mirror, a first interdigitated electrode, and a second interdigitated electrode. The top surface of the substrate is covered with a protective layer. The support structure is bonded to the top surface of the substrate. The torsion beam is fixedly connected to the support structure and suspended above the protective layer. The mirror is fixed in the middle of the torsion beam and is divided into a first part and a second part by the torsion beam. The first interdigitated electrode is located on the side of the first part away from the torsion beam. The first interdigitated electrode includes a first fixed electrode and a first movable electrode that are alternately distributed in sequence along the direction away from the first part and have uneven top surfaces. The second interdigitated electrode is located on the side of the second part away from the torsion beam. The second interdigitated electrode includes a second fixed electrode and a second movable electrode that are alternately distributed in sequence along the direction away from the second part and have uneven top surfaces. The first movable electrode and the second movable electrode are tilted by applying opposite driving forces, causing the mirror to rotate around the torsion beam by a preset angle.

[0006] The MEMS micromirror structure in the above embodiments can utilize a glass substrate, with the support structure, torsion beam, reflector, first interdigitated electrode, and second interdigitated electrode simultaneously fabricated on a silicon wafer. The thickness of the silicon wafer can then be freely controlled through thinning, reducing the thickness and volume of the MEMS micromirror structure. During the fabrication of the support structure, torsion beam, reflector, first interdigitated electrode, and second interdigitated electrode, the first and second interdigitated electrodes can be formed using composite mask etching. This allows for free control of the top surface height difference between the first fixed electrode and the first movable electrode, as well as the top surface height difference between the second movable electrode and the second fixed electrode, improving the flexibility of the MEMS micromirror structure design. Furthermore, the top surface height difference between the first and second movable electrodes creates a differential distribution. When driven, the first and second movable electrodes can apply opposing driving forces to the reflector, causing the reflector to tilt around the torsion beam at a predetermined angle. Because the first fixed electrode and the first movable electrode are alternately distributed and their top surfaces are not flush in the first interdigitated electrode, and the second fixed electrode and the second movable electrode are alternately distributed and their top surfaces are not flush in the second interdigitated electrode, compared to the first fixed electrode and the first movable electrode with flush top surfaces, and the second movable electrode and the second fixed electrode with flush top surfaces, this embodiment can drive the first movable electrode and the second movable electrode with a smaller driving voltage, causing the reflector to rotate around the torsion beam by a preset angle. Therefore, this embodiment can reduce the driving voltage used to drive the micromirror structure without increasing the volume of the fabricated product or providing the same driving force. The protective layer can not only avoid the adverse effects of etching and other processes on the substrate, but also reduce the complexity of subsequent bonding alignment. The support structure, torsion beam, reflector, first interdigitated electrode and second interdigitated electrode all adopt standard processes such as photolithography, etching and bonding, which have stronger process compatibility, lower process difficulty, and do not require the development of other supporting non-standard processes; the silicon wafer can be etched multiple times to form the MEMS micromirror structure, which can reduce the adverse effects of deep etching on the comb teeth or electrode surface.

[0007] According to some embodiments, the torsion beam includes a first end and a second end for fixed connection with a support structure, the torsion beam being located between the first end and the second end; the torsion beam extends along a first direction parallel to the top surface of the substrate; the MEMS micromirror structure further includes: a ground electrode disposed on the substrate, located on the side of the first end away from the torsion beam along the first direction; and a driving electrode disposed on the substrate, located on the side of the second end away from the torsion beam along the first direction, or located between the first end and the mirror.

[0008] According to some embodiments, a plurality of first interdigitated electrodes are arranged at intervals along a direction away from the first part; the first beams of the plurality of first interdigitated electrodes are all fixedly connected to the torsion beam via a first rod; the second beams of the plurality of first interdigitated electrodes are fixedly connected to the support structure; first movable electrodes are provided on the first beam at intervals along the extension direction of the first beam; first fixed electrodes are provided on the second beam at intervals along the extension direction of the second beam, and the first fixed electrodes and first movable electrodes with uneven top surfaces are alternately distributed in sequence along a direction away from the first part.

[0009] According to some embodiments, a plurality of second interdigitated electrodes are arranged at intervals along a direction away from the second part; the third beams of the plurality of second interdigitated electrodes are all fixedly connected to the torsion beam via second rods; the fourth beams of the plurality of second interdigitated electrodes are fixedly connected to the support structure; second movable electrodes are provided on the third beams at intervals along the extension direction of the third beams, and second fixed electrodes are provided on the fourth beams at intervals along the extension direction of the fourth beams; the second fixed electrodes and second movable electrodes with uneven top surfaces are alternately distributed in sequence along a direction away from the second part; the first rod is fixedly connected to the second end; the second rod is fixedly connected to the first end; the first rod is located between the two ends of it fixedly connected to the base; the second rod is located between the two ends of it fixedly connected to the base.

[0010] According to some embodiments, the two ends of the first rod are respectively fixedly connected to the base via corresponding first fixed anchors; the two ends of the second rod are respectively fixedly connected to the base via corresponding second fixed anchors.

[0011] According to some embodiments, the top surface of the first movable electrode is lower than the top surface of the first fixed electrode; the top surface of the second movable electrode is higher than the top surface of the second fixed electrode.

[0012] According to some embodiments, the top surface of the first movable electrode is higher than the top surface of the first fixed electrode; the top surface of the second movable electrode is lower than the top surface of the second fixed electrode.

[0013] According to some embodiments, the top surface of the first fixed electrode is flush with the top surface of the second movable electrode.

[0014] According to some embodiments, a second aspect of this application provides a method for fabricating a MEMS micromirror structure, comprising:

[0015] Provide a substrate to form a protective layer covering the target surface of the substrate;

[0016] A target layer is formed on a substrate. The target layer includes a support structure, a torsion beam, a reflector, a first interdigitated electrode, and a second interdigitated electrode. The support structure is bonded to the top surface of the substrate. The torsion beam is fixedly connected to the support structure and suspended above the protective layer. The reflector is fixed in the middle of the torsion beam and is divided into a first part and a second part by the torsion beam. The first interdigitated electrode is located on the side of the first part away from the torsion beam. The first interdigitated electrode includes a first fixed electrode and a first movable electrode that are alternately distributed in the direction away from the first part and have uneven top surfaces. The second interdigitated electrode is located on the side of the second part away from the torsion beam. The second interdigitated electrode includes a second fixed electrode and a second movable electrode that are alternately distributed in the direction away from the second part and have uneven top surfaces. The first movable electrode and the second movable electrode are tilted by applying opposite driving forces, causing the reflector to rotate around the torsion beam by a preset angle.

[0017] According to some embodiments, a target layer is formed on a substrate, including:

[0018] A silicon wafer is provided, the back side of which includes a first sacrificial layer for defining a micromirror anchor layer;

[0019] A first patterned photoresist layer is formed over the first sacrificial layer to define the back comb layer;

[0020] A back comb layer is formed within the silicon wafer based on the first patterned photoresist layer;

[0021] Based on the first sacrificial layer and the back comb layer, the silicon wafer is etched to obtain the silicon wall and support structure located directly below the first sacrificial layer, and the micromirror anchor layer surrounded by the silicon wall.

[0022] After removing the first sacrificial layer, the top surface of the silicon wall and the top surface of the supporting structure are bonded to the substrate, so that the silicon wall surrounds the protective layer.

[0023] After forming a mirror electrode on the front side of the thinned silicon wafer, a first patterned mask layer is formed to cover the mirror electrode;

[0024] The target layer is formed by etching the silicon wafer at least twice based on the first patterned mask layer.

[0025] According to some embodiments, the target surface is used to define a MEMS micromirror structure; a protective layer is formed covering the target surface of the substrate, including:

[0026] A first patterned photoresist layer is formed on the surface of the substrate after pretreatment, and the first patterned photoresist layer defines the target surface;

[0027] A metal layer is sputtered by magnetron sputtering, covering a first patterned photoresist layer and a target surface; the metal layer and the first patterned photoresist layer outside the target surface are removed, and the metal layer remaining on the target surface is used to form a protective layer. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1a This is a top view schematic diagram of a MEMS micromirror structure provided in some embodiments;

[0030] Figure 1b A MEMS micromirror structure provided in some embodiments Figure 1a A schematic diagram of the longitudinal section structure obtained in the AA' direction is shown.

[0031] Figure 2 This is a schematic diagram of the fixing structure of a reflector and torsion beam in a MEMS micromirror structure provided in some embodiments;

[0032] Figure 3 This is a partial structural schematic diagram of a first fixed electrode, a first movable electrode, a second fixed electrode, and a second movable electrode of a MEMS micromirror structure provided in some embodiments;

[0033] Figure 4 This is a schematic diagram illustrating the working principle of the first movable electrode and the second movable electrode of a MEMS micromirror structure provided in some embodiments;

[0034] Figure 5 This is a schematic diagram of a MEMS micromirror structure fabrication method provided in some embodiments;

[0035] Figure 6a A schematic diagram of the cross-sectional structure of the structure obtained after forming the first patterned photoresist layer;

[0036] Figure 6b A schematic diagram of the cross-sectional structure of the structure after the metal layer is formed;

[0037] Figure 6c A schematic diagram of the cross-sectional structure of the resulting structure after the protective layer has been formed;

[0038] Figure 7 A schematic diagram of the cross-sectional structure of the structure obtained after forming the second patterned photoresist layer;

[0039] Figure 8 A schematic diagram of the cross-sectional structure of the structure obtained after forming the back comb layer;

[0040] Figure 9 A schematic diagram of the cross-sectional structure of the structure obtained after forming the micromirror anchor layer;

[0041] Figure 10 This is a schematic diagram of the cross-sectional structure of the structure obtained after bonding the silicon wafer to the substrate;

[0042] Figure 11 A schematic diagram of the cross-sectional structure of the structure obtained after forming the mirror electrode;

[0043] Figure 12 A schematic diagram of the cross-sectional structure of the resulting structure after the hard mask is formed;

[0044] Figure 13 A schematic diagram of the cross-sectional structure of the structure obtained after forming the fourth patterned photoresist layer;

[0045] Figure 14 A schematic diagram of the cross-sectional structure of the structure obtained after the formation of the front electrode layer;

[0046] Figure 15 A schematic diagram of the cross-sectional structure of the resulting MEMS micromirror structure.

[0047] Explanation of reference numerals in the attached figures:

[0048] 100. Substrate; 10. Silicon wafer; 101. Silicon wall; 102. Torsion beam; 102a. First end; 102b. Second end; 103. Mirror; 21. First interdigitated electrode; 211. First fixed electrode; 212. First movable electrode; 213. First beam; 214. Second beam; 22. Second interdigitated electrode; 221. Second fixed electrode; 222. Second movable electrode; 223. Third beam; 224. Fourth beam; 1031. First part; 1032. Second part; 104. Ground electrode; 105. Drive electrode; 106. First rod; 107. Second rod; 108. 109. First fixed anchor; 30. Second fixed anchor; 40. First sacrificial layer; 50. First patterned photoresist layer; 61. Back comb layer; 72. Micromirror anchor point layer; 83. Mirror electrode; PR1. First patterned photoresist layer; M11. Metal layer; M1. Protective layer; PR2. Second patterned photoresist layer; PR3. Third patterned photoresist layer; M21. Metal material layer; PR4. Fourth patterned photoresist layer; Y10. Hard mask; Y11. First patterned mask layer; Y1. Target mask layer; 80. Front electrode layer; 81. Lateral protrusion; 90. MEMS micromirror structure. Detailed Implementation

[0049] To facilitate understanding of this disclosure, a more complete description will now be given with reference to the accompanying drawings, in which preferred embodiments of the present disclosure are shown. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure.

[0051] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, regions, layers, doping types, and / or portions, these elements, components, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type, or portion from another element, component, region, layer, doping type, or portion. Therefore, without departing from the teachings of this invention, the first element, component, region, layer, doping type, or portion discussed below may be referred to as a second element, component, region, layer, or portion.

[0052] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0053] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms “comprise” and / or “comprising” are used in this specification, the presence of the stated feature, integer, step, operation, element, and / or part is established, but the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups is not excluded. Meanwhile, when used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0054] Embodiments of the invention are described herein with reference to cross-sectional views illustrating ideal embodiments (and intermediate structures) of the invention, thus allowing for the anticipation of variations in the shown shapes due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. The regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device, nor do they limit the scope of the invention.

[0055] MEMS micromirrors do not only move in simple in-plane horizontal motion, but often require vertical motion with higher manufacturing requirements and more complex structures. The driving comb teeth of MEMS micromirrors with torsional motion need to generate a vertical electric field force. Traditional driving comb teeth use teeth of equal height, which requires a large driving force to generate a vertical electrostatic force. Obviously, this design limits the improvement of MEMS micromirror performance and the reduction of size.

[0056] MEMS technology utilizes mature semiconductor mass production processes, such as photolithography, etching, and thin film deposition, to mass-produce miniaturized and integrated mechanical structures on silicon wafers. MEMS micromirrors leverage this technology to reduce the size of traditional optical mirrors by several orders of magnitude, achieving millimeter-level miniaturization. This gives MEMS micromirrors advantages such as small size, low power consumption, and high response speed.

[0057] Currently, there are two main fabrication processes for MEMS vertical comb-driven micromirrors:

[0058] One method utilizes silicon-on-insulator (SOI) technology, bonding multiple SOI wafers together and using a silicon dioxide layer as an etch stop layer to create comb teeth of varying heights. Alternatively, movable and fixed comb teeth can be defined on two different SOI wafers and driven by bonding. This SOI wafer-based processing method is costly, and the fixed thickness of the SOI wafer itself limits design and fabrication flexibility. Furthermore, the release of the SOI bulk silicon structure layer often involves wet etching of the silicon oxide layer. Due to capillary forces, delicate structures (such as comb teeth, mirrors, and substrate) are prone to adhesion failure, increasing process complexity and cost, and posing a high risk for small-sized structures. The photolithography of the front-side structure during the process uses double-sided alignment, further increasing process complexity and cost.

[0059] Another approach involves utilizing residual stress or applying external forces (such as electrostatic force or pressure) to post-process the etched structure, creating comb-like teeth of varying heights to fabricate MEMS micromirrors. Compared to SOI bulk silicon processes, this method effectively reduces the number of photolithography, etching, and bonding steps, thereby reducing process costs. However, in this method, process parameters significantly influence the residual stress of the MEMS micromirror, making it difficult to guarantee batch-to-batch consistency. Furthermore, the MEMS micromirrors fabricated using this method are no longer horizontal surfaces, making this process incompatible with other planar processes and limiting further integration of MEMS micromirrors with other devices.

[0060] To improve performance, it is essential to design MEMS micromirrors with unequal-height drive teeth. While single-ended unequal-height drive teeth are relatively simple to fabricate, the electrostatic driving force provided by this structure is limited, making it difficult to effectively improve MEMS micromirror performance. Therefore, the addition of double-ended unequal-height drive teeth is necessary to enhance MEMS micromirror performance. SOG (Solar Optical Gear) technology offers a simpler process flow and lower processing costs, and compared to SOI (Solar Injection) bulk silicon technology, it is easier to fabricate double-ended unequal-height drive teeth while also providing high process compatibility.

[0061] Based on this, this application aims to provide a MEMS micromirror structure and its fabrication method, which can reduce the driving voltage used to drive the micromirror structure without increasing the volume of the fabricated product or providing the same driving force.

[0062] Please refer to Figure 1a , Figure 1b and Figure 2 In some embodiments, a MEMS micromirror structure is provided, including a substrate 100, a support structure (not shown), a torsion beam 102, a reflector 103, a first interdigitated electrode 21, and a second interdigitated electrode 22. The top surface of the substrate 100 is covered with a protective layer M1; the support structure is bonded to the top surface of the substrate 100; the torsion beam 102 is fixedly connected to the support structure and suspended above the protective layer M1; the reflector 103 is fixed to the middle of the torsion beam 102 and is divided into a first part 1031 and a second part 1032 by the torsion beam 102; the first interdigitated electrode 21 is located in the first part 1031, facing away from the torsion beam 102. On one side, the first finger electrode 21 includes a first fixed electrode 211 and a first movable electrode 212 that are alternately distributed in a direction away from the first part 1031 and have uneven top surfaces; the second finger electrode 22 is located on the side of the second part 1032 away from the torsion beam 102, and the second finger electrode 22 includes a second fixed electrode 221 and a second movable electrode 222 that are alternately distributed in a direction away from the second part 1032 and have uneven top surfaces; the first movable electrode 212 and the second movable electrode 222 are tilted by applying opposite driving forces, causing the reflector 103 to rotate around the torsion beam 102 by a preset angle.

[0063] The MEMS micromirror structure in the above embodiments can utilize a glass substrate 100. The support structure, torsion beam 102, reflector 103, first interdigitated electrode 21, and second interdigitated electrode 22 are simultaneously fabricated on a silicon wafer. The thickness of the silicon wafer can then be freely controlled by thinning, reducing the thickness and volume of the MEMS micromirror structure. During the fabrication of the support structure, torsion beam 102, reflector 103, first interdigitated electrode 21, and second interdigitated electrode 22, the first interdigitated electrode 21 and second interdigitated electrode 22 can be formed using composite mask etching. This allows for free control of the top surface height difference between the first fixed electrode 211 and the first movable electrode 212, as well as the top surface height difference between the second movable electrode 222 and the second fixed electrode 221, improving the flexibility of the MEMS micromirror structure design. Furthermore, the first movable electrode 212 and the second movable electrode 222 have a height difference at their top surfaces, forming a differential distribution. When driven, the first movable electrode 212 and the second movable electrode 222 can apply opposing driving forces to the reflector 103, causing the reflector 103 to tilt around the torsion beam 102 by a preset angle. Since the first fixed electrode 211 and the first movable electrode 212 in the first interdigitated electrode 21 are alternately distributed and their top surfaces are not flush, and the second fixed electrode 221 and the second movable electrode 222 in the second interdigitated electrode 22 are alternately distributed and their top surfaces are not flush, compared to the first fixed electrode 211 and the first movable electrode 212 with flush top surfaces, and the second movable electrode 222 and the second fixed electrode 221 with flush top surfaces, this embodiment can drive the first movable electrode 212 and the second movable electrode 222 with a smaller driving voltage, causing the reflector 103 to rotate around the torsion beam 102 by a preset angle. Therefore, this embodiment can reduce the driving force used to drive the micromirror structure without increasing the volume of the manufactured product. The protective layer M1 not only prevents etching and other processes from adversely affecting the substrate 100, but also reduces the complexity of subsequent bonding alignment. The support structure, torsion beam 102, reflector 103, first interdigitated electrode 21, and second interdigitated electrode 22 all employ standard processes such as photolithography, etching, and bonding, which have stronger process compatibility, lower process difficulty, and do not require the development of other supporting non-standard processes; the silicon wafer can be etched multiple times to form the MEMS micromirror structure, which can reduce the adverse effects of deep etching on the comb teeth or electrode surface.

[0064] Please refer to Figure 2In some embodiments, the torsion beam 102 includes a first end 102a and a second end 102b for fixed connection with the support structure, and the torsion beam 102 is located between the first end 102a and the second end 102b; the torsion beam 102 extends along a first direction parallel to the top surface of the substrate 100; the MEMS micromirror structure also includes a ground electrode 104 disposed on the substrate 100, located on the side of the first end 102a away from the torsion beam 102 along the first direction; the driving electrode 105 is disposed on the substrate 100, located on the side of the second end 102b away from the torsion beam 102 along the first direction, or located between the first end 102a and the reflector 103.

[0065] Please refer to Figure 1a In some embodiments, a plurality of first interdigitated electrodes 21 are arranged at intervals along a direction away from the first part 1031; the first beams 213 of the plurality of first interdigitated electrodes 21 are all fixedly connected to the torsion beam 102 via the first rod 106; the second beams 214 of the plurality of first interdigitated electrodes 21 are fixedly connected to the support structure; the first beams 213 are provided with first movable electrodes 212 spaced apart along the extension direction of the first beams 213; the second beams 214 are provided with first fixed electrodes 211 spaced apart along the extension direction of the second beams 214, and the first fixed electrodes 211 and the first movable electrodes 212 with uneven top surfaces are alternately distributed in sequence along a direction away from the first part 1031.

[0066] Please refer to Figure 1a In some embodiments, a plurality of second interdigitated electrodes 22 are arranged at intervals along a direction away from the second part 1032; the third beams 223 of the plurality of second interdigitated electrodes 22 are all fixedly connected to the torsion beam 102 via the second rod 107; the fourth beams 224 of the plurality of second interdigitated electrodes 22 are fixedly connected to the support structure; the third beam 223 is provided with second movable electrodes 222 distributed at intervals along the extension direction of the third beam 223, and the fourth beam 224 is provided with second fixed electrodes 221 distributed at intervals along the extension direction of the fourth beam 224; the second fixed electrodes 221 and the second movable electrodes 222 with uneven top surfaces are alternately distributed in sequence along a direction away from the second part 1032; the first rod 106 is fixedly connected to the second end 102b; the second rod 107 is fixedly connected to the first end 102a; the first rod 106 is located between the two ends of it fixedly connected to the base 100; the second rod 107 is located between the two ends of it fixedly connected to the base 100.

[0067] Please continue to refer to this. Figure 1a In some embodiments, the MEMS micromirror structure is symmetrical about the torsion beam 102 as the axis of symmetry, forming a double-ended unequal height drive comb structure.

[0068] Please refer to Figure 2In some embodiments, the support structure may include a first fixed anchor 108 and a second fixed anchor 109. The two ends of the first rod 106 are respectively fixedly connected to the base 100 via the corresponding first fixed anchor 108; the two ends of the second rod 107 are respectively fixedly connected to the base 100 via the corresponding second fixed anchor 109.

[0069] Please refer to Figure 1b In some embodiments, the top surface of the first movable electrode 212 is lower than the top surface of the first fixed electrode 211; the top surface of the second movable electrode 222 is higher than the top surface of the second fixed electrode 221.

[0070] Please refer to Figure 3 In some embodiments, the top surface of the first movable electrode 212 is higher than the top surface of the first fixed electrode 211; the top surface of the second movable electrode 222 is lower than the top surface of the second fixed electrode 221.

[0071] Please refer to Figure 1b In some embodiments, the top surface of the first fixed electrode 211 is flush with the top surface of the second movable electrode 222.

[0072] Please refer to Figure 1b , Figure 4 In some embodiments, the top surface of the first movable electrode 212 is lower than the top surface of the first fixed electrode 211; the top surface of the second movable electrode 222 is higher than the top surface of the second fixed electrode 221. The first movable electrode 212 and the second movable electrode 222 can apply opposing driving forces to the reflector 103, driving the reflector 103 to tilt around the torsion beam 102 by a preset angle. In this embodiment, the first movable electrode 212 and the second movable electrode 222 can be driven with a smaller driving voltage, causing the reflector 103 to rotate around the torsion beam 102 by a preset angle. Therefore, this embodiment can reduce the driving force used to drive the micromirror structure without increasing the volume of the manufactured product.

[0073] In some embodiments, a method for fabricating a MEMS micromirror structure is provided, comprising:

[0074] Step S10: Provide a substrate and form a protective layer covering the target surface of the substrate;

[0075] Step S20: A target layer is formed on the substrate. The target layer includes a support structure, a torsion beam, a reflector, a first interdigitated electrode, and a second interdigitated electrode. The support structure is bonded to the top surface of the substrate. The torsion beam is fixedly connected to the support structure and suspended above the protective layer. The reflector is fixed in the middle of the torsion beam and is divided into a first part and a second part by the torsion beam. The first interdigitated electrode is located on the side of the first part away from the torsion beam. The first interdigitated electrode includes a first fixed electrode and a first movable electrode that are alternately distributed in the direction away from the first part and have uneven top surfaces. The second interdigitated electrode is located on the side of the second part away from the torsion beam. The second interdigitated electrode includes a second fixed electrode and a second movable electrode that are alternately distributed in the direction away from the second part and have uneven top surfaces. The first movable electrode and the second movable electrode are tilted when subjected to opposite driving forces, causing the reflector to rotate around the torsion beam by a preset angle.

[0076] Please refer to Figure 5 In some embodiments, step S20, forming the target layer on the substrate, includes:

[0077] Step S210: Provide a silicon wafer, the back side of which includes a first sacrificial layer for defining the micromirror anchor layer;

[0078] Step S220: Form a first patterned photoresist layer covering the first sacrificial layer to define the back comb layer;

[0079] Step S230: Based on the first patterned photoresist layer, a back comb layer is formed in the silicon wafer;

[0080] Step S240: Based on the first sacrificial layer and the back comb layer, the silicon wafer is etched to obtain the silicon wall and support structure located directly below the first sacrificial layer, and the micromirror anchor layer surrounded by the silicon wall.

[0081] Step S250: After removing the first sacrificial layer, bond the top surface of the silicon wall and the top surface of the support structure to the substrate so that the silicon wall surrounds the protective layer.

[0082] Step S260: After forming a mirror electrode on the front side of the thinned silicon wafer, a first patterned mask layer covering the mirror electrode is formed;

[0083] Step S270: Etch the silicon wafer at least twice based on the first patterned mask layer to form the target layer.

[0084] Please refer to Figures 6a-6c In some embodiments, the target surface is used to define the MEMS micromirror structure; step S10, forming a protective layer M1 covering the target surface of the substrate 100, includes:

[0085] Step S110: A first patterned photoresist layer PR1 is formed on the surface of the pretreated substrate 100, and the first patterned photoresist layer PR1 defines the target surface;

[0086] Step S120: Magnetron sputtering of metal layer M11, metal layer M11 covering first patterned photoresist layer PR1 and target surface; removing metal layer M11 and first patterned photoresist layer PR1 outside the target surface, and retaining metal layer M11 on the target surface to form protective layer M1.

[0087] Please refer to Figures 6a-6c In some embodiments, photoresist is spin-coated onto the surface of a pre-processed glass and photolithography is performed. The photoresist acts as a mask to etch the glass, resulting in... Figure 6a The structure is shown. Before spin-coating the photoresist, the pre-processed glass can be organically cleaned with acetone and ethanol, followed by cleaning with deionized water and drying to ensure the glass surface is free of dust, grease, contaminants, water, and other pollutants, thus ensuring the spin-coating effect and quality of the photoresist and improving the lithography quality. Next, the glass is placed in a vacuum oven, where an adhesive, such as hexamethyldisilazane (HMDS), is deposited on the surface to enhance the adhesion of the photoresist. Then, the glass is spin-coated with photoresist on a spin coater, followed by a pre-baking treatment. Finally, photolithography is performed on the lithography machine, followed by a post-baking treatment to obtain the first patterned photoresist layer PR1 with strong corrosion resistance. A targeted glass etching solution is used for etching the glass.

[0088] Please refer to Figure 6a In some embodiments, the glass thickness and the type and thickness of the photoresist can be appropriately set according to actual needs, and the etching depth can be determined according to the thickness of the protective layer. In this embodiment, the glass thickness can be set to 295μm-305μm, such as 295μm, 300μm, or 305μm, etc.; the thickness of the first patterned photoresist layer PR1 is 1.95μm-2.05μm, such as 1.95μm, 2.00μm, or 2.05μm, etc.; the etching solution can be hydrofluoric acid buffered etching solution BHF; the etching depth can be set to 245nm-255nm, such as 245nm, 250nm, or 255nm, etc.

[0089] Please refer to Figure 6b In some embodiments, a metal layer M11 is magnetron sputtered, covering the first patterned photoresist layer PR1 and the target surface. The metal layer M11 may include Ti, Pt, Au, or a combination thereof. For example, the metal layer M11 may be a composite metal layer of Ti, Pt, and Au, with a Ti layer thickness of 30 nm, a Pt layer thickness of 40 nm, and an Au layer thickness of 220 nm. This configuration allows the metal thickness to be greater than the trench depth, facilitating metal stripping without affecting subsequent anodic bonding steps.

[0090] Please refer to Figure 6cIn some embodiments, the metal layer M11 outside the target surface and the first patterned photoresist layer PR1 are removed, and the metal layer M11 remaining on the target surface is used to form a protective layer M1. The protective layer M1 not only avoids adverse effects on the substrate 100 from subsequent etching processes, but also reduces the complexity of subsequent bonding alignment. By first forming the first patterned photoresist layer PR1 that exposes the target surface, and then forming the metal layer M11 covering the first patterned photoresist layer PR1 and the target surface by magnetron sputtering, the metal layer M11 directly above the first patterned photoresist layer PR1 is removed simultaneously during the stripping and removal of the first patterned photoresist layer PR1, reducing the complexity and cost of the fabrication process.

[0091] Please refer to Figure 6c In some embodiments, acetone solution can be used to remove the first patterned photoresist layer PR1 and the metal layer M11 directly above it, leaving the metal layer M11 in the etching groove, thus avoiding etching the metal layer M11 directly above the target surface and reducing the complexity and cost of the fabrication process.

[0092] Please refer to Figure 7 In some embodiments, step S210 includes providing silicon wafer 10, comprising:

[0093] Step S221: A silicon dioxide layer is formed on the surface of the initial silicon wafer after pre-processing;

[0094] Step S222: Form a second patterned photoresist layer PR2 on the top surface of the silicon dioxide layer;

[0095] Step S223: Using the second patterned photoresist layer PR2 as a mask, etch the silicon dioxide layer to obtain the first sacrificial layer 30 used to define the micromirror anchor layer 62.

[0096] Please continue to refer to this. Figure 7 In some embodiments, in step S221, a silicon dioxide layer is formed on the surface of the initial silicon wafer after pre-processing. This can be achieved by first cleaning to remove any possible contaminants from the surface of the initial silicon wafer, followed by thermal oxidation of the initial silicon wafer to obtain a silicon wafer 10 with a silicon dioxide layer on its surface. In step S222, a second patterned photoresist layer PR2 is formed on the top surface of the silicon dioxide layer, and the second patterned photoresist layer PR2 is used as a mask to etch the silicon dioxide layer, resulting in... Figure 7The structure shown is then processed, followed by the removal of the photoresist. The thickness of the second patterned photoresist layer PR2 is 1.95μm-2.05μm, for example, 1.95μm, 2.00μm, or 2.05μm, etc. In step S223, BOE solution can be used to etch the silicon dioxide layer. BOE solution has a slow etching rate, allowing for precise control of etching time, reducing lateral etching, and improving process accuracy. After obtaining the first sacrificial layer 30, which defines the position, size, and shape of the silicon wall and support structure directly below it, the second patterned photoresist layer PR2 is organically removed using acetone and ethanol. Then, dry photoresist is removed in a dry photoresist stripper to reduce photoresist residue. Unless otherwise specified, the photoresist removal process in this step is preferred in subsequent steps.

[0097] Please refer to Figure 8 In some embodiments, in step S230, a first patterned photoresist layer 40 is formed covering the first sacrificial layer 30 to define the back comb layer 50. In step S240, based on the first patterned photoresist layer 40, the back comb layer 50 is formed within the silicon wafer 10. The height difference of the comb teeth can be designed according to the actual MEMS micromirror structure, thereby setting the etching depth in this embodiment. In this embodiment, the etching depth is 9.5μm-10.5μm, for example, 9.5μm, 10μm, or 10.5μm, etc.

[0098] Please refer to Figure 9 In some embodiments, in step S250, the silicon wafer 10 is etched based on the first sacrificial layer 30 and the back comb layer 50 to obtain the silicon wall 101 and support structure located directly below the first sacrificial layer 30, and the micromirror anchor layer 62 surrounded by the silicon wall 101.

[0099] Please continue to refer to this. Figure 9 In some embodiments, after forming the back comb layer 50, the first patterned photoresist layer 40 is removed; using the first sacrificial layer 30 and the back comb layer 50 as a mask, the silicon wafer 10 is etched a first target number of times to obtain the silicon wall 101 and support structure located directly below the first sacrificial layer 30, and the micromirror anchor layer 62 surrounded by the silicon wall 101. The anchor height is appropriately set according to the actual MEMS micromirror structure design; the first target number of times is related to the etching depth of the micromirror anchor layer 62 and the single etching depth. The anchor height is appropriately set according to the actual MEMS micromirror structure 90 design. In this embodiment, the etching depth adopts a step-by-step etching method, dividing the etching depth of the micromirror anchor layer 62 into multiple small etching depths for multiple etchings, reducing the impact of deep etching on the comb surface.

[0100] Please continue to refer to this. Figures 8-9In some embodiments, the etching depth of the micromirror anchor layer 62 is adopted by step etching, which is divided into multiple small etching depths for multiple etchings to reduce the impact of deep etching on the comb surface. In this embodiment, the etching depth of the micromirror anchor layer 62 can be set to 20μm. The total depth of 20μm can be divided into 5 etchings, each with an etching depth of 4μm.

[0101] Please refer to Figure 10 In some embodiments, in step S260, after removing the first sacrificial layer 30, the top surface of the silicon wall 101 and the top surface of the support structure are bonded to the substrate 100, so that the silicon wall 101 surrounds the protective layer M1. This facilitates further patterning of the silicon wafer 10 inside the silicon wall 101, resulting in a micromirror anchor layer 62 surrounded by the silicon wall 101. Thus, by using the top surface of the silicon wall 101 to bond to the substrate 100, the silicon wall 101 surrounds the back comb layer 50. The protective layer M1 can be used to avoid adverse effects on the substrate 100 by subsequent etching processes, and can also reduce the complexity of subsequent bonding alignment.

[0102] Please continue to refer to this. Figure 10 In some embodiments, the top surface of the silicon wall 101 is anoly bonded to the substrate 100, followed by thinning of the silicon wafer 10. Of course, before anoly bonding, to ensure the bonding success rate, the silicon wafer 10 and the glass can be subjected to dry adhesive removal and organic cleaning to reduce surface contamination. There are many options for thinning the silicon wafer 10 after bonding, such as using KOH solution to etch the silicon wafer 10 for thinning.

[0103] Please refer to Figure 11 In some embodiments, a mirror electrode 70 is formed on the front side of the thinned silicon wafer 10, including: after bonding the top surface of the silicon wall 101 to the substrate 100, wet etching and thinning the front side of the silicon wafer 10; forming a third patterned photoresist layer PR3 (not shown) on the front side of the thinned silicon wafer 10; magnetron sputtering a metal material layer M21 (not shown), the metal material layer M21 covering the third patterned photoresist layer PR3; removing the third patterned photoresist layer PR3 and the metal material layer M21 directly above it, the remaining metal material layer M21 being used to form the mirror electrode 70. The mirror electrode 70 can assist in the alignment steps in subsequent process steps. The metal material layer M21 may include Ti, Pt, Au, or combinations thereof, for example, the metal material layer M21 may be a composite metal layer of Ti, Pt, and Au, with a Ti layer thickness of 30 nm, a Pt layer thickness of 40 nm, and an Au layer thickness of 100 nm.

[0104] Please refer to Figure 12In some embodiments, a hard mask Y10 is deposited on the front side of the silicon wafer 10, covering the mirror electrode 70. Silicon dioxide can be deposited using plasma-enhanced chemical vapor deposition (PECVD) or aluminum can be deposited using magnetron sputtering as the hard mask Y10. In this embodiment, for example, silicon dioxide is deposited using PECVD as the hard mask Y10, and the hard mask Y10 has a thickness of 300 nm.

[0105] Please refer to Figure 12 In some embodiments, photoresist is spin-coated onto the top surface of the hard mask Y10, the hard mask Y10 is etched, and then the photoresist is removed to obtain a first patterned mask layer Y11 for defining the first interdigitated electrode 21, the reflector 103, and the second interdigitated electrode 22. For example, silicon dioxide can be etched using BOE solution to a depth of 300 nm.

[0106] Please refer to Figure 13 In some embodiments, a fourth patterned photoresist layer PR4 is formed on the top surface of the first patterned mask layer Y11; the fourth patterned photoresist layer PR4 is used to define the micromirror structure. The first patterned mask layer Y11 may include silicon dioxide. The thickness of the first patterned mask layer Y11 may be 250 μm-400 μm. For example, the thickness of the first patterned mask layer Y11 may be 250 μm, 300 μm, 350 μm, or 400 μm, etc.

[0107] Please refer to Figure 14 In some embodiments, the first patterned mask layer Y11 and the silicon wafer 10 are etched using the fourth patterned photoresist layer PR4 as a mask to obtain the front electrode layer 80. The remaining first patterned mask layer Y11 is used to form the target mask layer Y1. The etching depth is appropriately set according to the design requirements of the MEMS micromirror structure, for example, the etching depth is 20 μm.

[0108] Please refer to Figure 15 In some embodiments, the front electrode layer 80 is etched using the fourth patterned photoresist layer PR4 as a mask, at least removing the lateral protrusions 81 of the front electrode layer 80 to form a MEMS micromirror structure 90, wherein the lateral direction is parallel to the flush surface of the silicon wafer. This etching process employs a step-by-step etching method to reduce the impact of deep etching on the comb tooth surface. In this embodiment, a total etching depth of 10 μm is preferably achieved through two etching passes, each with a depth of 5 μm. The protective layer can be made of metal, which can adsorb etching ions, preventing them from damaging the comb tooth morphology.

[0109] Please refer to Figure 15 In some embodiments, a wet process is used to etch away the target mask layer Y1.

[0110] Please continue to refer to Figure 1- Figure 15 The MEMS micromirror structure and its fabrication method in the above embodiments have at least the following unexpected technical effects:

[0111] Using a glass substrate 100, a support structure, a torsion beam 102, a reflector 103, a first interdigitated electrode 21, and a second interdigitated electrode 22 are simultaneously fabricated on a silicon wafer. The thickness of the silicon wafer can then be freely controlled by thinning, reducing the thickness and volume of the MEMS micromirror structure. During the fabrication of the support structure, torsion beam 102, reflector 103, first interdigitated electrode 21, and second interdigitated electrode 22, the first interdigitated electrode 21 and the second interdigitated electrode 22 can be formed using composite mask etching. This allows for free control of the height difference between the top surfaces of the first fixed electrode 211 and the first movable electrode 212, as well as the height difference between the top surfaces of the second movable electrode 222 and the second fixed electrode 221, improving the flexibility of the MEMS micromirror structure design. Furthermore, the first movable electrode 212 and the second movable electrode 222 have a height difference at their top surfaces, forming a differential distribution. When driven, the first movable electrode 212 and the second movable electrode 222 can apply driving forces in opposite directions to the reflector 103, causing the reflector 103 to tilt around the torsion beam 102 by a preset angle. Since the first fixed electrode 211 and the first movable electrode 212 in the first intercalation electrode 21 are alternately distributed and their top surfaces are not flush, and the second fixed electrode 221 and the second movable electrode 222 in the second intercalation electrode 22 are alternately distributed and their top surfaces are not flush, compared to the first fixed electrode 211 and the first movable electrode 212 with flush top surfaces, and the second movable electrode 222 and the second fixed electrode 221 with flush top surfaces, this embodiment can drive the first movable electrode 212 and the second movable electrode 222 with a smaller driving voltage, causing the reflector 103 to rotate around the torsion beam 102 by a preset angle. Therefore, this embodiment can reduce the driving voltage used to drive the micromirror structure without increasing the volume of the fabricated product or providing the same driving force. The protective layer M1 not only avoids adverse effects of etching and other processes on the substrate 100, but also reduces the complexity of subsequent bonding alignment. The support structure, torsion beam 102, reflector 103, first interdigitated electrode 21, and second interdigitated electrode 22 all use standard processes such as photolithography, etching, and bonding, which have stronger process compatibility, lower process difficulty, and do not require the development of other supporting non-standard processes; the silicon wafer can be etched multiple times to form the MEMS micromirror structure, which can reduce the adverse effects of deep etching on the comb teeth or electrode surface.

[0112] Although Figure 5The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the exact order indicated by the arrows. Unless otherwise specified in this document, there is no strict order in which these steps are executed, and they can be executed in other sequences. Moreover, although Figure 5 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution of these sub-steps or stages is not necessarily sequential, but can be performed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0113] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] The embodiments described above are merely illustrative of several implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these modifications and improvements all fall within the scope of protection of this disclosure.

Claims

1. A MEMS micromirror structure, characterized in that, include: A substrate, the target surface of which is covered with a metal protective layer; the metal protective layer is used to reduce the alignment complexity of subsequent bonding steps; the target surface is used to define the MEMS micromirror structure; a support structure is bonded to the top surface of the substrate; A torsion beam, fixedly connected to the supporting structure, is suspended above the protective layer; A reflector is fixed to the middle of the torsion beam and is divided into a first part and a second part by the torsion beam; The first interdigitated electrode is located on the side of the first part away from the torsion beam. The first interdigitated electrode includes a first fixed electrode and a first movable electrode that are alternately distributed along the direction away from the first part and whose top surfaces are not flush. The second interdigitated electrode is located on the side of the second part away from the torsion beam. The second interdigitated electrode includes a second fixed electrode and a second movable electrode that are alternately distributed along the direction away from the second part and whose top surfaces are not flush. The top surface of the first fixed electrode is flush with the top surface of the second movable electrode. The support structure, the torsion beam, the reflector, the first interdigitated electrode, and the second interdigitated electrode are fabricated simultaneously on the substrate. The protective layer is used to adsorb etching ions during the simultaneous formation of the first interdigitated electrode and the second interdigitated electrode in the same etching process to avoid damaging the electrode morphology. The first movable electrode and the second movable electrode are tilted by applying opposite driving forces, causing the reflector to rotate around the torsion beam by a preset angle.

2. The MEMS micromirror structure according to claim 1, characterized in that, The torsion beam includes a first end and a second end for fixed connection with the support structure, and the torsion beam is located between the first end and the second end. The torsion beam extends along a first direction parallel to the top surface of the base; The MEMS micromirror structure also includes: A grounding electrode is disposed on the substrate, located on the side of the first end away from the torsion beam along the first direction; The driving electrode is disposed on the substrate, located on the side of the second end away from the torsion beam along the first direction, or located between the first end and the reflector.

3. The MEMS micromirror structure according to claim 2, characterized in that, A plurality of first interdigitated electrodes are arranged at intervals along a direction away from the first part; the first beams of the plurality of first interdigitated electrodes are all fixedly connected to the torsion beam via a first rod; the second beams of the plurality of first interdigitated electrodes are fixedly connected to the support structure. The first beam is provided with first movable electrodes that are spaced apart along the extension direction of the first beam; The second beam is provided with first fixed electrodes that are spaced apart along the extension direction of the second beam. The first fixed electrodes and the first movable electrodes, whose top surfaces are not flush, are alternately distributed in a direction away from the first part.

4. The MEMS micromirror structure according to claim 3, characterized in that, Multiple second interdigitated electrodes are arranged at intervals in a direction away from the second part; the third beams of the multiple second interdigitated electrodes are all fixedly connected to the torsion beam via the second rod; the fourth beams of the multiple second interdigitated electrodes are fixedly connected to the support structure. The third beam is provided with second movable electrodes spaced apart along the extension direction of the third beam, and the fourth beam is provided with second fixed electrodes spaced apart along the extension direction of the fourth beam. The second fixed electrodes and the second movable electrodes with uneven top surfaces are alternately distributed in a direction away from the second part. The first rod is fixedly connected to the second end; The second rod is fixedly connected to the first end; The first rod is located between its two ends, which are fixedly connected to the base; The second rod is located between its two ends, which are fixedly connected to the base.

5. The MEMS micromirror structure according to claim 4, characterized in that, The two ends of the first rod are respectively fixedly connected to the base via corresponding first fixed anchors; The two ends of the second rod are respectively fixedly connected to the base via corresponding second fixed anchors.

6. The MEMS micromirror structure according to any one of claims 1-5, characterized in that, The top surface of the first movable electrode is lower than the top surface of the first fixed electrode; The top surface of the second movable electrode is higher than the top surface of the second fixed electrode.

7. The MEMS micromirror structure according to any one of claims 1-5, characterized in that, The top surface of the first movable electrode is higher than the top surface of the first fixed electrode; The top surface of the second movable electrode is lower than the top surface of the second fixed electrode.

8. A method for fabricating a MEMS micromirror structure, characterized in that, include: A substrate is provided, and a metal protective layer is formed covering the target surface of the substrate; the metal protective layer is used to reduce the alignment complexity of subsequent bonding steps; the target surface is used to define the MEMS micromirror structure; A target layer is formed on the substrate. The target layer includes a support structure, a torsion beam, a reflector, a first interdigitated electrode, and a second interdigitated electrode. The support structure is bonded to the top surface of the substrate. The torsion beam is fixedly connected to the support structure and suspended above the protective layer. The reflector is fixed to the middle of the torsion beam and is divided into a first part and a second part by the torsion beam. The first interdigitated electrode is located on the side of the first part away from the torsion beam and includes a first fixed electrode and a first movable electrode that are alternately distributed along the direction away from the first part and have uneven top surfaces. The second interdigitated electrode is located on the side of the second part away from the torsion beam. The interdigitated electrode includes a second fixed electrode and a second movable electrode that are alternately distributed along a direction away from the second part and whose top surfaces are not flush; the first movable electrode and the second movable electrode are tilted by applying opposite driving forces, causing the reflector to rotate around the torsion beam by a preset angle; the top surface of the first fixed electrode is flush with the top surface of the second movable electrode; the support structure, the torsion beam, the reflector, the first interdigitated electrode, and the second interdigitated electrode are simultaneously fabricated on the substrate; the protective layer is at least used to adsorb etching ions during the simultaneous formation of the first interdigitated electrode and the second interdigitated electrode in the same etching process, so as to avoid damaging the electrode morphology.

9. The method for fabricating a MEMS micromirror structure according to claim 8, characterized in that, Forming a target layer on the substrate, comprising: A silicon wafer is provided, the back side of which includes a first sacrificial layer for defining a micromirror anchor layer; A first patterned photoresist layer is formed over the first sacrificial layer to define the back comb layer; Based on the first patterned photoresist layer, the back comb layer is formed within the silicon wafer; Based on the first sacrificial layer and the back comb layer, the silicon wafer is etched to obtain a silicon wall and support structure located directly below the first sacrificial layer, and a micromirror anchor layer surrounded by the silicon wall. After removing the first sacrificial layer, the top surface of the silicon wall is bonded to the substrate, so that the silicon wall surrounds the protective layer; After forming a mirror electrode on the front side of the thinned silicon wafer, a first patterned mask layer is formed to cover the mirror electrode; The target layer is formed by etching the silicon wafer at least twice based on the first patterned mask layer.

10. The method for fabricating a MEMS micromirror structure according to claim 9, characterized in that, The protective layer forming the target surface covering the substrate includes: After pretreatment, a first patterned photoresist layer is formed on the surface of the substrate, and the first patterned photoresist layer defines the target surface; A magnetron sputtered metal layer is formed, which covers the first patterned photoresist layer and the target surface; the metal layer and the first patterned photoresist layer outside the target surface are removed, and the metal layer remaining on the target surface is used to form the protective layer.

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